The expression of cytochrome P450 enzymes in human breast tumours and normal breast tissue

Environmental chemicals are one of the risk factors in breast cancer genesi s. Cytochrome P450 (CYP) enzymes play a major role in the activation of the se chemicals. Using highly specific and sensitive reverse transcriptase-pol ymerase chain reaction (RT-PCR) analysis, the expression profile of all maj or xenobiotic metabolizing CYP forms was screened in breast tumour and surr ounding tumour free (control) breast tissue in a series of 20 sample pairs obtained from females with infiltrating ductal carcinoma. The levels of CYP 1A1 mRNA were very low in both tumour and normal tissue. CYP1B1, CYP2B6, CY P2C, CYP2D6, CYP2E1, CYP4B1, and CYP11A1 expressions were positive in both tumours and control tissue. CYP2A6, CYP2A7, CYP2A13, CYP2F1, CYP3A4, CYP3A5 , and CYP3A7 mRNAs were expressed neither in tumours nor in control tissue. These results show that several CYPs, responsible for the activation of a quite large number of procarcinogens and genotoxic estrogen metabolites, ar e expressed in breast tissue with a lack of qualitative differences in CYP expression at mRNA level between breast tumours and surrounding normal brea st.